Microstructure-magnetic shielding development in additively manufactured Ni-Fe-Mo soft magnet alloy in the as fabricated and post-processed conditions

This study introduces a deep analysis, which correlates the metallurgical characters with the magnetic properties in laser powder bed fusion processed Ni-Fe-Mo, to produce 3D prototypes with maximum magnetic shielding performance for ultra-sensitive quantum-based systems. The study conducts a sequenced plan of optimising the magnetic properties via microstructure density control, controlling the magnetic anisotropy, before applying heat treatment (HT) and hot isostatic pressing (HIP) post-processes. This is also considering delivering effective mechanical properties. The magnetic properties optimisation was performed via laser parametric study, which found that the sample built with laser energy density E = 4.68 J/mm² achieves the best soft magnetic and mechanical results due to the lowest defects. However, the obtained magnetic properties are still poor, due to the (001) rich grain orientation, which parallels the hard axis of magnetisation<100> in this alloy. It was found that tilting the crystallographic orientation of the as fabricated (AF) optimised condition with 45˚ and 35˚, with respect to the build direction, improves the soft magnetic properties, as these angles correspond to the easy axes of magnetisation<110>and<111>, respectively, allowing the grain orientation in the same directions. The magnetic properties are further promoted with HT and HIP post-processes application. The magnetic shielding results of hollow tubes, built with the same optimised condition, confirmed the magnetic behaviour of the bulk coupons, achieving 83% of the commercial magnetic shielding.